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Old 22 July 2015, 08:36   #11
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My best guess here is that the engine will have been tilted for towing? In which case all conventional carb float valve logic goes out the window, as gravity also plays a significant part i nthe ioperatio nof that valve. Coupled with the ambient level in the carb being at 45 degrees or so to "normal".

Fuel takns if the breather is shut and properly sealed (I guess you donlt have Hulk tanks? ) then the expansion of the air with the heat of the sun as you tow could be enough to auto pump. The only thing stopping it is the float valve which as above is about as much use a sa chocolate teapot at that angle.


Re. the explosion, depending how much had been pumped into the cowl and depending on where it pooled / ran when the engine was moved to "operating angle" there is a starter with a sparky set of brushes, and could also have been a backfire.....


I would agree with checking your electrics, but also look for scorch marks roud the inlet passages too.....



I guess you may have an older version of mine. There is no air filter per se, but should probably be an air box?

If it's a "Brown stripe" livery on the cowl, does the top of the cowl attach to an open square box? that could be an air filter?

You got a pic? if it's the vintage I think it is the air intake body holds the cowl on! - Mr Boatjumbles in Bellshill (google will find his number) has one breaking for spares at the moment....... I'm going to collect a bit for a decrepit Johnson tonight or tomorrow, I can ask if he still has the air box if you want.
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Old 23 July 2015, 11:31   #12
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Thanks

Guys,

Thanks very much for the replies. Stripped down the carbs and head, thereafter removing a mound of fire extinguisher powder!!

Found there to be a good bit of dirt and grit in the float chamber and fuel filter. All cleaned up and engine seems to fire up nicely, no pun intended.

Doing a full check over the electrics, making sure no bare wires / exposed areas just to be on the safe side. It's looking like the float has been jammed on, the fuel has been connected, and has filled up the carbs etc with extra fuel. Hence the start up has managed to cause a backfire and ignited the fumes.

Giving the engines a good few test runs on dry land and a good going over so fingers crossed il get it in the water and it will progress further than the foreshore!

Thanks again!
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Old 23 July 2015, 12:27   #13
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You did well not to ruin it with the extinguisher powder (especially if there's no air filter). They don't half make a mess!
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Old 24 July 2015, 02:43   #14
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In future it might make sense to remove the cowling when you arrive at the slip (after towing) to allow any vapours / fuel under there to evaporate before starting her up for the first time? Once she's running pop the cowling back on.
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Old 24 July 2015, 15:09   #15
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Quote:
Originally Posted by Superjetjim View Post
In future it might make sense to remove the cowling when you arrive at the slip (after towing) to allow any vapours / fuel under there to evaporate before starting her up for the first time? Once she's running pop the cowling back on.
Adding air doesn't seem a good plan. Venting does if you don't trust the engine, but I'd put the hood back on before starting if it was me...
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